Try giving them a good shake before hanging them. Hold them from the top and snap them in front of you so they make a noise. Does that make sense? That helps them to dry a little more smoothly and also to get a bit softer. Also, if they dry faster in the hot sun I think they get a bit stiffer than if there is a breeze to keep them moving. One other thing that really helps but is a hassle is to dry them a few minutes in the dryer first. Not sure if you have a dryer or not. It still saves you a lot on energy usage but is a bit of a pain to have to do that and then get them on the line. For some reason it works better than putting them in the dryer after they are dry.